Glycoproteins are important constituents of the cell surface of all mammalian cells, both normal and abnormal, many of which serve as antigens in autologous, syngeneic and xenogeneic immunizations. They have been implicated in many other properties of cell which involve specific recognition and interactions. The main objective of this study is to analyze the surface glycoproteins of cultured cells from malignant melanoma and other tumors. Two antigens of melanoma will be studied: Gp110 and DR or Ia-like antigens. The former, which is detected by a specific rabbit antiserum, appears to be the major glycoprotein of a number of cell types, both normal and malignant. Its significance lies in the possibility that it may exhibit structural differences in carbohydrate chains in malignant as compared to normal cells. Ia antigens were originally considered to be confined to cells of the hematopoietic system but have recently been found to occur on other cells including melanoma. Several aspects of the expression of Ia tumors will be studied: (1) quantitation of Ia antigen in different melanoma lines in melanoma tumors and in other tissues and cells, both normal and abnormal: (2) structural characteristics of melanoma Ia antigen; and (3) comparison of melanoma Ia with lymphocyte Ia cells derived from the same individual. The significance of Ia expression in melanoma lies in its possible role as a differentiation antigen and in influencing the immune response to the tumor. Studies on the cell surface glycoproteins of renal cancer cells will continue. Utilizing monoclonal antibodies, variations in the carbohydrate structures of specific glycoproteins will be characterized.